This invention relates to faulted current indicators, and particularly to methods and means for displaying a faulted current condition while ignoring temporary overloads and transients.
Faulted current indicators (or FCI's or fault indicators) are placed at intervals along power lines to disclose that a fault has occurred between the indicator and a load. In general, each FCI trips in response to an overcurrent that occurs as a result of a fault between the indicator and the load. The FCI remains in the trip indicating condition even after a current protection device, such as a circuit breaker or a fuse, has responded to the overcurrent by opening the line and ending the current in the line. After the fault has been cured and the current protection device closed to re-energize the line, the FCI resets in response to a minimum operating current.
Such devices often respond unintentionally to temporary overloads and transients. This creates a false indication which prevents maintenance crews from properly caring for the line.
One way of minimizing false operation of FCIs is to set their trip rating abnormally high to allow for transients and temporary overloads. This approach of making the FCIs less responsive trades away the sensitivity of the FCIs to low level currents.